Display active alignment systems utilizing test patterns for calibrating signals in waveguide displays

ABSTRACT

A display system includes a display alignment tracker configured track the position of a first signal in a first waveguide and the position of a second signal in a second waveguide. The display alignment tracker optically multiplexes a portion of a first signal and a portion of the second signal into a combined optical signal and measures a differential between the first signal and the second signal. The differential is used to adjust the position, dimensions, or a color attribute of the first signal relative to the second signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

N/A

BACKGROUND Background and Relevant Art

Computers and computing systems have affected nearly every aspect ofmodern living. Computers are generally involved in work, recreation,healthcare, transportation, entertainment, household management, etc.Computers commonly present information to a user in a visual manner. Thepresentation of visual information to users can be performed through avariety of technologies. Conventional monitors and screens presentvisual information to users on a flat surface in the user's environment,such as a desktop monitor, a smartphone screen, or a laptop display.

Virtual reality systems present visual information to users with ahead-mounted display, which incorporates one or more motion and/orposition sensors to simulate an artificial visual environment. Virtualreality systems present visual information as the environment. Toreplicate a visual environment, the virtual reality system can presentdifferent visual information on a plurality of visual channels, suchdifferent visual information to left and right eyes.

Augmented or mixed reality system present visual information to userswith a head-mounted display by overlaying and/or integrating the visualinformation with the user's ambient environment. For example, a mixedreality system may present visual information in the form of a simulatedobject on a table surface. To accurately represent the position of thesimulated object to the user, separate visual signals are presented tothe user to create a depth of field of the simulated object and allowthe user to perceive the position of the object in space.

The accurate simulation of one or more objects in a user's ambientenvironment relies upon the relative position of the first signal (i.e.,the visual information presented to the user's left eye) and the secondsignal (i.e., the visual information presented to the user's right eye).Precise identification of alignment and/or displacement of the differentvisual signals presented to a user is, therefore, desirable.

The subject matter claimed herein is not limited to embodiments thatsolve any disadvantages or that operate only in environments such asthose described above. Rather, this background is only provided toillustrate one exemplary technology area where some embodimentsdescribed herein may be practiced.

BRIEF SUMMARY

Disclosed embodiments include methods for display alignment tracking forhead-mounted devices. The disclosed methods include sampling a firstsignal from a first waveguide, sampling a second signal from a secondwaveguide, optically combining the signals and detecting one or moretest patterns within the combined optical signals. The locations of thetest pattern obtained from the combined signal are used to identifydifferentials between the first and the second signals.

Disclosed embodiments also include systems for tracking signal alignmentin waveguides. Some of the disclosed embodiments include at least onedisplay module assembly, a first waveguide, a second waveguide, anoptical multiplexer, an imaging sensor, one or more processors incommunication with the imaging sensor, and one or more computer readablemedia having stored thereon instructions that are executable by the oneor more processors. The display module assembly is configured to providea first signal and a second signal. The first waveguide is configured toguide the first signal therethrough. The second waveguide is configuredto guide the second signal therethrough. The optical multiplexer isconfigured to combine at least a portion of the first signal and atleast a portion of the second signal. The imaging sensor is configuredto receive a combined signal from the optical multiplexer that includesat least a portion of the first signal and at least a portion of secondsignal. The instructions are executable to receive at least a portion ofthe first signal and at least a portion of the second signal from theimaging sensor, to identify a first pattern included in the first signaland a second pattern included in the second signal, and to compare atleast physical positioning of the first pattern relative to at leastphysical positioning of the second pattern.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

Additional features and advantages will be set forth in the descriptionwhich follows, and in part will be obvious from the description, or maybe learned by the practice of the teachings herein. Features andadvantages of the invention may be realized and obtained by means of theinstruments and combinations particularly pointed out in the appendedclaims. Features of the present invention will become more fullyapparent from the following description and appended claims, or may belearned by the practice of the invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otherfeatures of the disclosure can be obtained, a more particulardescription will be rendered by reference to specific embodimentsthereof which are illustrated in the appended drawings. For betterunderstanding, the like elements have been designated by like referencenumbers throughout the various accompanying figures. While some of thedrawings may be schematic or exaggerated representations of concepts, atleast some of the drawings may be drawn to scale. Understanding that thedrawings depict some example embodiments, the embodiments will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIG. 1 is a schematic front view of an embodiment of a head-mounteddisplay system;

FIG. 2 is a rear perspective view of an embodiment of a frame of thedisplay system of FIG. 1;

FIG. 3 is a top schematic view of an embodiment of a display alignmentsystem of the display system of FIG. 1;

FIG. 4 is a schematic representation of embodiments of sampling regionsof a display pixel array;

FIG. 5 is a schematic representation of embodiments of sampling regionsincluding test patterns of a display pixel array;

FIG. 6 is a schematic representation of other embodiments of samplingregions including test patterns of a display pixel array;

FIG. 7 is a schematic representation of another embodiment of samplingregion of a display pixel array

FIG. 8 is a flowchart illustrating an embodiment of a method ofoptically multiplexing a portion of a first signal and a portion of asecond signal;

FIG. 9 is a flowchart illustrating an embodiment of a method ofadjusting a portion of a first signal and a portion of a second signalin response to calculating a differential;

FIG. 10 is a schematic representation of an embodiment of a displaysystem;

FIG. 11 is a flowchart illustrating an embodiment of a method ofverifying alignment between a portion of a first signal and a portion ofa second signal;

FIG. 12 is a flowchart illustrating an embodiment of a method ofcomparing color levels between a portion of a first signal and a portionof a second signal;

FIG. 13 is a flowchart illustrating an embodiment of a method ofrendering test patterns in a portion of a first signal and a portion ofa second signal;

FIG. 14 is a flowchart illustrating an embodiment of a method ofshifting pixels of a first signal relative to a second signal inresponse to calculating a differential;

FIG. 15 is a flowchart illustrating an embodiment of a method ofrendering a test pattern in a first signal and a second signal inresponse to a tagged image frame;

FIG. 16 is a flowchart illustrating an embodiment of a method ofrendering a test pattern in a first signal and a second signal inresponse to a tagged image frame; and

FIG. 17 is a flowchart illustrating an embodiment of a method of a DMAconcurrently adjusting position and color balance of a first signalrelative to a second signal.

DETAILED DESCRIPTION

This disclosure generally relates to devices, systems, and methods fordetecting alignment of visual information. More particularly, thepresent disclosure relates to measuring a difference between a firstvisual signal and a second visual signal in a head-mounted device. Thepresent disclosure also relates to the measurement and compensation ofphysical displacement or other differences (e.g., color) between a firstvisual signal and a second visual signal relative to one another.

The following discussion refers to a number of methods and method actsthat may be performed. Although the method acts may be discussed in acertain order or illustrated in a flow chart as occurring in aparticular order, no particular ordering is required unless specificallystated, or required because an act is dependent on another act beingcompleted prior to the act being performed.

Referring now to FIG. 1, an embodiment of a display system 100 isillustrated. In some embodiments, the display system 100 is ahead-mounted display, as shown in FIG. 1. In other embodiments, adisplay system according to the present disclosure may be any displaysystem that presents a plurality of visual signals to a user. Thedisplay system 100 of FIG. 1 has a body 102 that supports a frame 104with a first waveguide 106 and a second waveguide 108 therein.

The body 102 also houses and/or supports one or more computer componentsin communication with one another, such as processors, data storagedevices, communication devices, memory devices, power supplies, othercomputer components, or combinations thereof. For example, the body 102may support one or more processors in communication with a data storagedevice having instructions stored thereon that the one or moreprocessors may execute to perform the methods of the disclosedinvention.

The frame 104 supports at least a first waveguide 106 and a secondwaveguide 108. The first waveguide 106 and second waveguide 108 arepositioned to direct visual information to a user, such as beingpositioned in front of the user's eyes. In at least one embodiment, thefirst waveguide 106 is positioned in front of the user's left eye andthe second waveguide 108 is positioned in front of the user's right eye.

The first waveguide 106 and the second waveguide 108 are in opticalcommunication with a first display module assembly (DMA) 110 and asecond DMA 112, respectively. The first DMA 110 provides visualinformation to the first waveguide 106 and the second DMA 112 providesvisual information to the second waveguide 108. The DMA emits light thatis collimated and angularly encoded such that the center of a pixel onthe microdisplay equates to a specific angle in space. The exact anglesare defined by the focal length and distortion of the DMA collimatinglens and also other intrinsic characteristics of the system, such theorientation of the microdisplay and fold mirrors within the DMA. A firstsignal is provided to the first waveguide 106, for example, by the firstDMA 110. A second signal is provided to the second waveguide 108, forexample, by the second DMA 112. Discrepancies between an azimuth angle,elevation angle, or roll angle of the first signal provided by the firstDMA 110 and the azimuth angle, elevation angle, or roll angle of thesecond signal provided by the second DMA 112 may appear to a user asmisalignments of images in the first signal and second signal.

In other embodiments, the display system 100 may have a single DMA thatis in optical communication with both the first waveguide 106 and thesecond waveguide 108. In such an alternative embodiment, the single DMAtransmits separate signals to the separate waveguides.

The first signal propagates through the first waveguide 106 by internalreflection within the first waveguide 106. The second signal propagatesthrough the second waveguide 108 by internal reflection with the secondwaveguide 108. In some embodiments, the first waveguide 106 and/or thesecond waveguide 108 is a single optically transmissive layer. Forexample, the first waveguide 106 and/or second waveguide 108 may be asingle layer of glass. In other embodiments, the first waveguide 106and/or the second waveguide 108 comprises a stack of waveguides. Forexample, the first waveguide 106 and/or the second waveguide 108 may bea stack of waveguides wherein each of the waveguides is configured topropagate a particular range of wavelengths within that waveguide of thewaveguide stack.

The first waveguide 106 and second waveguide 108 each include adiffraction optical element (DOE) positioned on the waveguide tooutcouple visual information from the waveguide. In some embodiments, aDOE is positioned on the nasal edge (e.g., near the nose of the user) ofthe first waveguide 106 and/or the second waveguide 108. In otherembodiments, a DOE is positioned along a top edge of the first waveguide106 and/or the second waveguide 108. In at least one embodiment, each ofthe first waveguide 106 and the second waveguide 108 includes a separateDOE positioned at or near the top of the nasal side of the firstwaveguide 106 and the second waveguide 108, respectively, shown in FIG.1 as DOE 114 and 116. The first DOE 114 samples the first signal of thefirst waveguide 106 and the second DOE 116 samples the second signal ofthe second waveguide 108.

As shown in FIG. 2, a display alignment tracking (DAT) sensor 118 ispositioned proximate an output surface 120 of the first waveguide 106and the second waveguide 108. The input surface of the first waveguide106 and the second waveguide 108 faces away from the user and receivesambient light from the user's environment. The first waveguide 106 andthe second waveguide 108 mix the ambient light with the first signal andthe second signal to provide mixed reality visual information to a userviewing the mixed reality visual information proximate the outputsurface 120 of the first waveguide 106 and/or the second waveguide 108.

The DAT sensor 118 is positioned on the output surface 120 (e.g., theuser viewing side of the display system 100). Accordingly, the DATsensor 118 receives the first signal and second signal from the firstwaveguide 106 and the second waveguide 108 from the output surface 120as the user also views the first signal and the second signal from theoutput surface 120. In some embodiments, the DAT sensor 118 is supportedby the frame 104. In other embodiments, the DAT sensor is integratedinto the frame 104. In yet other embodiments, the DAT sensor 118 ispositioned adjacent the frame 104 and is supported by a body of thedisplay system 100.

FIG. 3 illustrates a top partial cross-sectional view of the nasal sidesof the first waveguide 106 and the second waveguide 108 with the DATsensor 118 positioned adjacent the output surface 120 of the firstwaveguide 106 and the second waveguide 108. The first signal 124 and thesecond signal 126 propagate through the first waveguide 106 and thesecond waveguide 108, respectively, and the first DOE 114 and the secondDOE 116 outcouple the first signal 124 and the second signal 126,respectively.

The DAT sensor 118 includes an optical sensor 128 that is configured toreceive a combined optical signal 130 of the first signal 124 and secondsignal 126. The DAT sensor 118 includes an optical multiplexer 132 thatmultiplexes the first signal 124 and the second signal 126. The opticalmultiplexer 132 combines the first signal 124 and second signal 126 withany appropriate optical hardware. In some embodiments, for example, theoptical multiplexer includes at least a first prism 134 and a secondprism 138 that multiplex the received signals by refracting both of thesignals towards a common optical sensor. In other embodiments, theoptical multiplexer 132 includes one or more fiber optic members tocombine the first signal 124 and second signal 128. In yet otherembodiments, the optical multiplexer 132 comprises a combination of oneor more prisms, fiber optic members, mirrors, and/or lenses. Forexample, an optical multiplexer 132 may direct a first signal 124 fromthe first DOE 114 to the first prism 134 by one or more fiber opticmembers. In another example, the optical multiplexer 132 may direct thefirst signal 124 from the first prism 134 to the second prism 138 by oneor more fiber optic members. The optical multiplexer 132 directs thefirst signal 124 from the first prism 134 to the second prism 138through an optical medium, such as glass or one or more fiber opticmembers, to introduce the first signal 124 into the second prism 138without refraction occurring at the first interface of the second prism.

In some embodiments, the optical sensor 128 may be a single pixeloptical sensor. For example, the optical sensor may detect a periodicstructure presented in a certain phase through an aperture, and theoptical sensor may sense the integrated power of the periodic structure.In other embodiments, the optical sensor 128 includes a plurality ofphotoreceptors in a photoreceptor array. For example, the optical sensor128 may be an imaging sensor. In some embodiments, the optical sensor128 is a charge coupled device (CCD). In other embodiments, the opticalsensor 128 is a complimentary metal-oxide sensor (CMOS).

In some embodiments, the optical sensor 128 includes a plurality ofchannels on which different colors may be received. For example, theoptical sensor 128 may have red, green, and blue channels or yellow,cyan, and magenta channels (i.e., configured to detect and/or recordlight in red, green, and blue wavelengths or yellow, cyan, and magentawavelengths). In other examples, the optical sensor 128 may have visiblewavelength channels and infrared wavelength channels. In otherembodiments, the optical sensor 128 has a photoreceptor array that isconfigured to receive signal on a single channel. For example, theoptical sensor 128 may have a blue channel. In other examples, theoptical sensor 128 may have an infrared channel configured to receivelight in infrared wavelengths.

In some embodiments, positioning of the DAT sensor 118 is at leastpartially dependent on a displacement 136 of the first DOE 114 andsecond DOE 116. The displacement 136 may be in a range having an uppervalue, a lower value, or an upper and lower value including any of 3millimeters (mm), 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12mm, 13 mm, 14 mm, 15 mm, or any values therebetween. In some instances,the displacement 136 is greater than 3 mm. In other instances, thedisplacement 136 is less than 15 mm. In yet other instances, thedisplacement 136 is within a range of between about 3 mm and about 15 mmand even more preferably within a range of between about 5 mm and about12 mm. In at least one example, the displacement 136 is at or about 9mm.

The DAT sensor 118 includes a first prism 134 and a second prism 138. Insome instances, the spacing between the first prism 134 and the secondprism 138 is equivalent to the displacement 136 of the first DOE 114 andsecond DOE 116. In other embodiments, the spacing between the firstprism 134 and the second prism 138 is more than displacement 136 or lessthan displacement 136. For example, the first signal 124 and/or secondsignal 126 may exit the first waveguide 106 and/or second waveguide 108at a non-perpendicular angle. The first prism 134 and second prism 138,therefore, are positioned to receive the first signal 124 and secondsignal 126, respectively, as the first signal 124 and second signal 126are outcoupled from the first waveguide 106 and second waveguide 108 bythe first DOE 114 and second DOE 116.

The first prism 134 refracts the first signal 124 at any angle such thatthe first signal 124 is directed toward the second prism 138. Forexample, the first prism 134 may refract the light at an angle in arange having an upper value, a lower value, or an upper and lower valueincluding any of 45°, 60°, 75°, 90°, 105°, 120°, 135°, or any valuestherebetween. In some instances, the first prism 134 refracts the lightat an angle greater than 45°. In other instances, the first prism 134refracts the light at an angle less than 135°. In yet other instances,the first prism 134 refracts the light in a range between about 45° andabout 135° and, even more particularly, within a range of between about75° and about 105°. In at least one example, the first prism 134refracts the light at or about 90°.

The second prism 138 refracts the second signal 126 and transmits thefirst signal 124 through the second prism 138 such that a combinedoptical signal 130 is directed at and received by the optical sensor128. In some embodiments, the first prism 134 is positioned a firstprism distance 140 from the optical sensor 128. The first prism distance140 may be in a range having an upper value, a lower value, or an upperand lower value including any of 15 mm, 17 mm, 19 mm, 20 mm, 21 mm, 22mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, or anyvalues therebetween. In some instances, the first prism distance 140 isgreater than 15 mm. In other instances, the first prism distance 140 isless than 30 mm. In yet other examples, the first prism distance 140 iswithin a range between about 15 mm and about 30 mm and even moreparticularly between about 20 mm and about 26 mm. In at least oneexample, the first prism distance 140 is at or about 24 mm.

In some embodiments, the second prism 138 is positioned a second prismdistance 142 from the optical sensor 128. The second prism distance 142may be in a range having an upper value, a lower value, or an upper andlower value including any of 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm,12 mm, 13 mm, 14 mm, 15 mm, any values therebetween. In some instances,the second prism distance 142 is greater than 5 mm. In other examples,the second prism distance 142 is less than 15 mm. In yet other examples,the second prism distance 142 is in a range between about 5 mm and about15 mm and even more preferably between about 7 mm and about 13 mm. In atleast one example, the second prism distance 142 is at or about 10 mm.

To capture and/or sample at least a portion of the combined opticalsignal 130, the optical sensor 128 may have a sensor width 144 in arange having an upper value, a lower value, or upper and lower valuesincluding any of 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm,10 mm, or any values therebetween. In some instances, the sensor width144 is greater than about 1 mm. In other examples, the sensor width 144is less than about 10 mm. In yet other examples, the sensor width 144 isin a range between about 1 mm and about 10 mm. In further examples, thesensor width 144 is in a range between about 3 mm and about 7 mm. In atleast one example, the sensor width 144 is at or about 5 mm.

The DAT sensor, according to the present disclosure, is operable tosample any desired portion of the combined optical signal, which mayinclude any portion of the first signal and the second signal. As notedabove, the first signal and second signal are generated by the first DMAand the second DMA, respectively. For instance, the first DMA and secondDMA generate the first signal and second signal, respectively, using adisplay pixel array, such as a liquid crystal on silicon (LCOS) pixelarray in each of the first DMA and the second DMA.

An example display pixel array 146 and associated signal is shown inFIG. 4 through FIG. 7. The display pixel array 146 has a plurality ofpixels in an active region 148 used to generate visual informationintended for a user and a plurality of pixels in a border region 150that are intended to provide a buffer of pixel space. The border region150 allows a DMA to move the active region 148 to accommodate and/orcompensate for misalignments in the mechanical construction of thedisplay system.

FIG. 4 illustrates an embodiment of a display pixel array 146 withexamples of various sampling regions overlaid upon the display pixelarray 146. A sampling region is the portion of the signal sampled and/orimaged by the DAT sensor. For example, the DAT sensor may be configuredto sample only a portion of the signal provided to the DAT sensor. Asshown in FIG. 4, the DAT sensor may sample a sampling region 152 (i.e.,152-1, 152-2 and/or 152-3) of the combined optical signal without anyadditional test pattern being imposed on the images to detectedalignment between the first signal portion of the combined opticalsignal and the second signal portion of the combined optical signal, asdisclosed in more detail below.

In some embodiments, the sampling region 152-1 is entirely within theactive region 148 of the signal from the display pixel array 146, inwhich case the image contained in the signal is sampled and used todetect alignment and/or other signal attributes. In other embodiments,the sampling region 152-2 is partially within the active region 148 andpartially within the border region 150, exposing a single edge/border ofthe active region that is usable to detect alignment between the sampledsignal. In yet other embodiments, the sampling region 152-3 is partiallywithin the active region 148 and partially within the border region 150,exposing at least two edges/borders of the active region (e.g., both ahorizontal edge and a vertical edge of the active region 148) that arevisible within the sampling region 152-3, and such that bothedges/borders are usable to detect alignment of the sampled signal.

In some embodiments, the first signal and second signal also include atest pattern that allows for the DAT sensor to search for alignment ofthe test pattern of the first signal and second signal. As shown in FIG.5, the test pattern 154-1 may be within the active region 148 of thesignal from the display pixel array 146. The sampling region 152-4 maysample the active region 148 with the test pattern 154-1 and at least aportion of the border region 150. In other embodiments, a samplingregion 152-5 samples the region 148, including a test pattern 154-2,without sampling the border region 150.

As shown in FIG. 6, a test pattern 154-3, 154-4 may be located in theborder region 150. For example, a test pattern 154-3 is shown in theborder region 150 with a sampling region 152-6 located to sample theborder region 150, the active region 148, the test pattern 154-3, andthe boundary between the active region 148 and the border region 150. Inanother example, a test pattern 154-4 is positioned in the border region150 and the sampling region 152-7 is positioned to sample the testpattern 154-4 and border region 150 without sampling the active region148. In at least one embodiment, a sampling region 152-8 includes all ofthe active region 148, as shown in FIG. 7. The sampling region 152-8 mayinclude at least a portion of the border region 150 or may include nopart of the border region 150.

FIG. 8 illustrates a flowchart 800 corresponding to methods foroptically multiplexing optical signals from two separate waveguidesmounted to a head-mounted display. As reflected, these methods includesampling a first signal from a first waveguide (810), sampling a secondsignal from a second waveguide (820), and optically multiplexing atleast a portion of the first signal and at least a portion of the secondsignal to create a combined optical signal (830).

In some embodiments, the first signal is sampled with a first DOEpositioned on the first waveguide and the second signal is sampled witha second DOE positioned on the second waveguide. The optical multiplexermay include a prism assembly, a fiber optic assembly, or other opticalassembly to combine and/or overlay at least a portion of the firstsignal and at least a portion of the second signal. The opticalmultiplexer may direct the combined optical signal to an optical sensorto image the combined optical signal.

The first signal and second signal may be generated by a display pixelarray and/or a DMA, as described herein. Sampling the first signal andsampling the second signal may include using a sampling region thatincludes an active region, a border region, or a combination thereof, asshown in relation to FIG. 4 through FIG. 7. In some embodiments, thesampling region used in sampling 158 the first signal and sampling thesecond signal includes a test pattern.

FIG. 9 illustrates another flowchart 900 that corresponds to otherrelated methods for adjusting visual information based on opticallymultiplexing optical signals from two separate waveguides mounted to ahead-mounted display, which is related to the methods described inrelation to the FIG. 8. For example, the flowchart 900 illustrates howthe disclosed methods include sampling a first signal from a firstwaveguide (910), sampling a second signal from a second waveguide (920),and optically multiplexing at least a portion of the first signal and atleast a portion of the second signal to create a combined optical signal(930) and then extracting a test pattern from the first signal and thesecond signal (940). In some embodiments, the test pattern is located inan active region of the first signal and second signal. In otherembodiments, the test pattern is located in a border region of the firstsignal and second signal. In yet other embodiments, the test pattern islocated at least partially in the border region and at least partiallyin the active region of the first signal and second signal.

The flowchart 900 also includes acts of detecting a differential betweenthe first signal and the second signal in at least a physical positionassociated with a first rendering location of the test pattern extractedfrom the first signal and a second rendering location of the testpattern extracted from the second signal (950) and adjusting renderingof at least the first signal and the second signal to at least partiallycompensate for the detected differential (960).

In some embodiments, the detection of a differential between the firstsignal and the second signal includes comparing a first coordinate valueof the first rendering location of the test pattern extracted from thefirst signal and a second coordinate value of the second renderinglocation of the test pattern extracted from the second signal. Forexample, the first coordinate value may have an azimuth value, anelevation value, and a roll value within the first signal and the secondcoordinate value may have an azimuth value, an elevation value, and aroll value within the second signal. In an embodiment in which there isnegligible or no displacement between the first signal and the secondsignal, the first coordinate value and second coordinate value will beequivalent. In other embodiments, the first coordinate value and secondcoordinate value differ in at least one of the azimuth value, elevationvalue, or roll value.

A coordinate value differential between the first signal and secondsignal may indicate a displacement of the first signal in the firstwaveguide relative to the second signal in the second waveguide. Thisdisplacement can be measured and used to adjust presentation of thefirst or second signal, to thereby improve alignment of the signals, asdescribed in more detail below. In other embodiments, the DAT sensordetects an absolute differential, such as a linear distance differentialbetween the perceived first signal and second signal.

In some embodiments, the detection of a differential between the firstsignal and the second signal includes comparing a first dimensionalvalue of the first rendering location of the test pattern extracted fromthe first signal and a second dimensional value of the second renderinglocation of the test pattern extracted from the second signal. Thedimensional value of the test pattern preferably includes a combinationof the x-displacement and y-displacement of the test pattern in thesignal (although it may also be limited to only the x-displacement ory-displacement of the test pattern).

When the dimensional value includes a combination of the x-displacementand y-displacement, the first dimensional value may have an azimuthvalue, an elevation value, and a roll value within the first signal andthe second coordinate value may have an azimuth value, an elevationvalue, and a roll value within the second signal. In an embodiment inwhich there is no displacement between the first signal and the secondsignal, the first dimensional value and second dimensional value areequivalent. In other embodiments, the first dimensional value and seconddimensional value differ in at least one of the azimuth value, elevationvalue, and roll value. A dimensional differential in the test patternbetween the first signal and second signal may indicate a distortion inthe first signal in the first waveguide relative to the second signal inthe second waveguide.

In some embodiments, adjusting rendering of at least the first signaland the second signal (960) is based at least partially on the detecteddifferential. For example, a coordinate differential in the test patternis used to displace the first signal in azimuth, elevation, or roll suchthat the coordinate value of the first rendering location of the testpattern extracted from the first signal and the coordinate value of thesecond rendering location of the test pattern extracted from the secondsignal are equivalent. In another example, a dimensional differential inthe test pattern is used to stretch the first signal in the azimuth,elevation, or roll such that the dimensional value of the firstrendering location of the test pattern extracted from the first signaland the dimensional value of the second rendering location of the testpattern extracted from the second signal are equivalent.

In some embodiments, the test pattern is a test pattern imposed on thefirst signal and second signal. In other embodiments, the test patternis a sampling region of the first signal and second signal in which aportion of the active region, a portion of the border region, a boundarybetween the active region and the border region, or combinations thereofis the test pattern.

Attention will now be directed to FIGS. 10A and 10B, which illustratesome of the components that are incorporated within the discloseddisplay systems for enabling the methods described herein.

FIG. 10A shows a display system 1000 that includes one or more DMA(s)1010 with corresponding display pixel array(s) 1020 (e.g., 146 of FIG.4) that generate the first and second signals, respectively, aspreviously described above. For the purposes of illustration, the firstand second DMA are collectively identified as DMA(s) 1010 and thecorresponding display pixel array(s) are identified as element 1020 inFIG. 10A. It will be understood that the first and second DMAs and thecorresponding display pixel arrays are configured to run in parallel andto communicate in parallel with the DAT 1030, as previously describedabove in reference to FIG. 3.

The DAT 1030 includes an optical multiplexer 1032 in communication withan image sensor 1034 to receive a combined optical signal from theoptical multiplexer 1032. The DAT 1030 is in data communication withother computing components 1040 including at least one CPU 1042 incommunication with a data storage device 1044. The data storage devicemay include physical computer-readable storage media. Physicalcomputer-readable storage media includes RAM, ROM, EEPROM, CD-ROM orother optical disk storage (such as CDs, DVDs, etc.), magnetic diskstorage or other magnetic storage devices, or any other medium which canbe used to store desired program code means in the form ofcomputer-executable instructions or data structures and which can beaccessed by a general purpose or special purpose computer. Inparticular, the computer memory may store computer-executableinstructions that when executed by one or more processors cause variousfunctions to be performed, such as the acts recited in the embodimentsof methods described herein.

In some embodiments, the computing components 1040 further include acommunication device 1046. The communication device 178 may include anycombination of wired and/or wireless communication hardware and/orsoftware, including a universal serial bus, Ethernet, Bluetooth, Wi-Fi,and/or other wired or wireless communication components.

The DAT 1030 and/or computing components 1040 may determine thedifferential between the first signal and the second signal. Thedifferential is used to displace and/or stretch the rendering of thefirst signal and/or the second signal. Data regarding the first andsecond signals is provided to the corresponding first and second DMAs1010 by an application-specific integrated circuit (ASIC) 1050.

The ASIC 1050 includes one or more processors that are applicationspecific to one or more functions of the display system 100. Forexample, one or more processors of the ASIC 1050 may include audioprocessors, accelerometers, gyroscopes, power management systems, otherapplication-specific processors, or combinations thereof.

A software-on-chip (SOC) 1070 and/or graphical processor unit (GPU) 1080may calculate information regarding the first and second signals andprovide the information to the ASIC 1050, the computing components 1040,or any combination thereof. The ASIC 1050, the computing components1040, or any combinations thereof may also use the differentialcalculated by the DAT 1030 and/or computing components 1040 to alter thedata prior to the rendering of additional/altered first and secondsignals. The ASIC 1050, the computing components 1040, or anycombinations thereof may then provide the data to the first and secondDMAs 1010 to render the corresponding first and secondadditional/altered signals. The display systems 1000A and 1000B,therefore may operate as a feedback loop that samples the first andsecond signals rendered by the DMAs 1010, calculates a differentialbetween at least a portion of the first signal and at least a portion ofthe second signal, and uses the differential to adjust the rendering offurther frames of the first signal and/or second signal by the first andsecond DMAs 1010, respectively.

In some embodiments, one or more adjustments to the first signal and/orsecond signal based on the detected differential between the sampledsignals are made in by the computing components 1040. In otherembodiments, one or more adjustments to the first signal and/or secondsignal based on the differential are made in the ASIC 1050. In yet otherembodiments, one or more adjustments to the first signal and/or secondsignal based on the differential are made in the GPU 1080.

Attention will now be directed to some of the disclosed methods forcalibrating the first and second signals based on the sampling describedabove.

The flowchart 1100 of FIG. 11, for instance, reflects a method thatincludes sampling a first signal from a first waveguide (1110), samplinga second signal from a second waveguide (1120), and opticallymultiplexing at least a portion of the first signal and at least aportion of the second signal to create a combined optical signal (1130).The reflected method further includes detecting a test pattern of thefirst signal and a test pattern of the second signal (1140).

As described herein, the test pattern may be a test pattern imposed onthe image frame, such as a test pattern 154-1 in an active region (asdescribed in relation to FIG. 5) or a test pattern 154-3 in a borderregion (as described in relation to FIG. 6). In other embodiments, thetest pattern is at least a portion of the active region, the borderregion, or the boundary between the active region and the border regionwithin the sampling region, as described in relation to FIG. 4.

The method shown in FIG. 11 further includes comparing physicalpositions (i.e., coordinate values) of the test pattern of the firstsignal and the test pattern of the second signal (1050). In someembodiments, comparing the physical positions includes calculating adifferential, such as a coordinate differential and/or a dimensionaldifferential, described herein. In other embodiments, comparing thephysical positions include determining wherein the test pattern of thefirst signal and the test pattern of the second signal are in the samephysical position within the first signal and the second signal,respectively. For example, when the coordinate differential is within0.1 mrad in the azimuth, elevation, roll, or combinations thereof andthe dimensional differential is within 0.1 mrad in the azimuth,elevation, roll, or combinations thereof, the first signal and secondsignal may be aligned. When the first signal and the second signal arealigned, the display system may perform further acts to verify one ormore other conditions of the display system.

By way of example, as shown in FIG. 12, the display system may alsoevaluate one or more color values of the first signal and second signal.For example, the method illustrated by flowchart 1200, which alsoincludes the acts of the flowchart 1100 of FIG. 11, further includescomparing color levels of the first signal and the second signal (1260).

In some embodiments, comparing color levels of the first signal and thesecond signal includes calculating a color spectrum of the first signaland the second signal. The color spectrum may be for a signal channel ora combination of channels of the first signal and the second signal. Forexample, the first signal and the second signal may be a series of colorsequential frames in each of a different color channel. The first signalmay consist of a red frame, a blue frame, and a green frame that arerendered in sequence, and a user may perceive the three color channelsas a single image frame. In other examples, more than one color channelmay be generated by a display pixel array simultaneously such that asingle image frame includes more than one color channel. In yet otherexamples, the first signal and second signal may include a red frame, ablue frame, and a green frame that are rendered in sequence with thefirst DMA rendering a first color channel of the first signal and thesecond DMA rendering a second color channel (i.e., a different colorfrom the first color channel) of the second signal. In such an example,the first signal and second signal are integrated over time to integratean equivalent full-spectrum frame before comparing color levels of thefirst signal and the second signal.

In other embodiments, comparing color levels of the first signal and thesecond signal includes calculating a color spectrum and/or measuring acolor uniformity of the test pattern extracted from the first signal andthe test pattern extracted from the second signal. For example, the testpattern may have known color balances or a known color spectrum to allowthe display system to more precisely compare the color balance and/orcolor uniformity of the first signal and the second signal. In at leastone example, the test pattern includes at least a portion that is red,at least a portion that is blue, at least a portion that is green, andat least a portion that is yellow.

FIG. 13 illustrates a flowchart 1300 depicts another method thatincludes acts of the flowchart 1100 described in relation to FIG. 11, aswell as some additional acts. For instance, the method shown in theflowchart 1300 of FIG. 13 includes the acts of providing a test pattern(1310) and rendering an image frame in a first signal and a secondsignal (1320). Providing a test pattern includes accessing one or morestored test patterns stored in a storage device of the display system ordetecting and selecting a portion of a provided image frame.

In some embodiments, providing a test pattern includes accessing a datastorage device of the display system and incorporating the test patterninto the data provided to the first and/or second DMA (such as describedin relation to FIG. 10A and 10B). Providing the test pattern furtherincludes positioning the test pattern within the image frame. Forexample, the test pattern may be positioned in the active region, theborder region, or a combination thereof.

The method also includes rendering the frame in a first signal and asecond signal. For example, a frame of the first signal and a frame ofthe second signal may be rendered simultaneously with a test pattern inthe first signal and the second signal. In other examples, as describedin relation to FIG. 12, the first signal and second signal may includecolor sequential frames. The test frame in which the test pattern isrendered may be related to the color of the frame, and therefore, thetest pattern may be rendered at a different time in the first signalthan in the second signal. In such embodiments, the DAT may integrate aplurality of frames of the first signal and the second signal beforedetecting a test pattern of the first signal and a test pattern of thesecond signal.

The test pattern is provided or sampling region is selected at varioustimes during usage of the display system. For example, a test patternmay be generated in an image frame at a time during usage that does notinterrupt or alter the user's experience. In an example, the testpattern is startup logo or other image provided during a startupprocedure. In another example, the test pattern is a system menuinitiated by the user and that is overlaid on an image frame. The systemmenu may have known dimensions and location, allowing the display systemto compare the physical location of one or more parts of the system menuin the first signal and the second signal. The system menu is alsoinitiated by the user, allowing the display system to generate a testpattern without interrupting the user's experience in an unexpectedmanner.

In other embodiments, the test pattern is provided during an instant inwhich a user will not perceive the test pattern on the image frame. Forexample, the display system may provide the test pattern and/or renderthe test pattern in response to a trigger from the display system. Thetrigger may be a physical trigger or the trigger may be a visualtrigger.

A physical trigger may include a trigger from an accelerometer, agyroscope, another movement measurement device, or combinations thereofin the display system. For example, during rapid rotation of a user'shead, the user's vision may temporarily be compromised or blurred. Thedisplay system can render or otherwise provide the test pattern inresponse to detecting a predetermined movement, such as the start ofrotational acceleration of the head-mounted display, and render orotherwise provide the test pattern during the movement.

A visual trigger may include a trigger from an external camera or othermachine vision of the display system. For example, sampling region ofthe first signal and the second signal sampled by the DAT, as describedherein, includes the first signal and the second signal generated by thefirst DMA and second DMA, respectively, with little or no ambient lightfrom the surrounding environment. In contrast, the user perceives thefirst signal and the second signal mixed with the ambient light by thefirst waveguide and the second waveguide.

In at least one embodiment, the display system may render or otherwiseprovide a test pattern that is visible to the DAT but notdistinguishable from the environment surrounding the user. For example,the display system may render or otherwise provide a test pattern in ablue channel when the display system recognizes the user is looking ator the head-mounted display is oriented toward the sky. In otherexamples, the display system may render or otherwise provide a testpattern in a red channel when the display system recognizes the user islooking at or the head-mounted display is oriented toward a red surface,such as a red brick wall. In such embodiments, the test pattern isunique to within the first signal and the second signal generated by thefirst DMA and second DMA, respectively, while being imperceptible whenviewed against the ambient environment.

Referring now to FIG. 14, a flowchart 1400 illustrates a method ofcalibrating the position of the first signal and the second signal. Theflowchart 1400 includes the steps of the flowchart 1100 described inrelation to FIG. 11 and the additional act of shifting pixels of theframe (1150). In some embodiments, shifting pixels of the frame includesadjusting data to the first DMA and/or second DMA to move the activeregion of the first signal and/or the second signal in the display pixelarray. For example, the amount the active region of the first signaland/or the second signal is moved can be based at least partially uponthe differential described in relation to FIG. 9.

In some embodiments, the differential may be less than a pixel. Asubpixel shift may be perceptible to a user, and a subpixel shift may beimplemented by shifting the intensity of neighboring pixels withoutshifting the entire image rendering by a full pixel. For example, aconventional head-mounted display or near-eye display may retain analignment between a first waveguide or display and a second waveguide ordisplay to within approximately 4 milliradian (mrad). For a user toperceive a single, integrated image from the head-mounted display ornear-eye display, the first signal and second signal should be within1.0 to 1.5 mrad.

In some embodiments, shifting pixels of the frame is performed in thecomputing components. In other embodiments, shifting pixels of the frameis performed in the ASIC. In yet other embodiments, shifting pixels ofthe frame is performed in the GPU.

In at least one embodiment, the display system may receive image framesfrom the SOC, the GPU, or the computing system of which the displaysystem may be unable to view the content. For example, there may bedigital copyright protections on certain video files that prevent one ormore components of the display system from analyzing the content ofparticular frames. Therefore, at least a portion of the first signal andthe second signal may be a predetermined signal. The display system haslimited control over the rendering of the image frames of thepredetermined signal. The display system may overlay visual informationto the image frames of the predetermined signal while remaining agnosticto the content of the image frames.

For example, FIG. 15 illustrates a flowchart 1500 of an embodiment of amethod for calibrating a first signal relative to a second signal duringdisplay of a predetermined signal. The flowchart 1500 includes the actsof the flowchart 1100 described in relation to FIG. 11, while alsoincluding acts for providing a known test pattern. The method includestagging image frames (1510) and providing a test pattern in response todetecting the tagged image frames (1520). For example, one or more imageframes of the predetermined signal may be provided by the SOC and/or theGPU. At least one of the image frames is tagged by the ASIC and/or GPUin the metadata of the image frame before being sent to DMA.

The DMA reads the metadata of each image frame sent to the DMA to berendered for the first signal and the second signal. When the DMAdetects a tagged image frame in the metadata, the DMA provides a testpattern to the image frame when rendering the image frame in the firstsignal and the second signal.

In some embodiments, at least one of the image frames is tagged by theASIC and/or GPU at periodic time intervals. For example, an image framemay be tagged every 1 second, every 10 seconds, every 1 minute, every 10minutes, etc. to verify alignment of the first signal and second signal.In other embodiments, the image frame of the predetermined signalincludes metadata that is recognized to tag the image frame. Forexample, during a video file, an image frame may include metadataindicating a chapter break in the video. The chapter break metadata canbe used to tag the image frame. In other embodiments, the DMA mayrecognize the chapter break in the video as a tagged image frame.

In other embodiments, other metadata in the predetermined signal is usedto tag one or more image frames. For example, the metadata for an imageframe may include information regarding the color balance and/orspectrum of the image frame. The display system may provide a testpattern when the color balance of the image frame is within a thresholdof a predetermined color balance and/or spectrum. For example, thedisplay system may recognize a black frame from a color balance and/orspectrum in the metadata and tag that frame in the metadata.

In further embodiments, a display system according to the presentdisclosure may evaluate similar portions of a first signal and a secondsignal to verify and adjust the color balance of the first signal andthe second signal. FIG. 16 illustrates a flowchart 1600 of an embodimentof a method for adjusting the color of a first signal and/or a secondsignal. The flowchart 1600 includes the steps of the flowchart 1100described in relation to FIG. 11 to verify the first signal and secondsignal are aligned before identifying a color attribute (1660) andcalculating a color differential (1670). The color differential is thenused in adjusting a color of the first signal and/or the second signal(1680).

In some embodiments, a color attribute is a percentage of a colorspectrum in a color range. In other embodiments, a color attribute is atotal intensity of the color spectrum. In yet other embodiment, a colorattribute is a relative intensity of a first color channel to secondcolor channel. In further embodiments, the color attribute is relativeintensity of a first color in a first portion of the image frame to thesame first color in a second portion of the image frame.

The color differential may be difference in the color attribute of thefirst signal and the second signal. In some embodiments, calculating thecolor differential is performed with a portion of the first signal and aportion of the second signal. In other embodiments, the colordifferential is calculated using the entire image frame of the firstsignal and the entire image frame of the second signal.

The color differential is then used in adjusting the color of the firstsignal and/or the second signal. For example, if the color differentialindicates that the red saturation is 5% less in the first signal than inthe second signal, the display system may increase the red saturation inthe first DMA by 5% (e.g., by increasing the drive current of an LEDarray and/or a display pixel array) to balance the color attributes ofthe first signal and the second signal.

In at least one embodiment, a display system may verify and/or correctfor both image displacement and color imbalances substantiallyconcurrently. For example, FIG. 17 is a flowchart 1700 of a method thatmay be performed by the DMA. The method includes receiving testpattern(s) (1710) and/or receiving image frame(s) (1720). In someembodiments, the DMA receives a plurality of test patterns that may beimplemented in different situations.

For example, the method further includes detecting tagged frames (1730)and rendering (1740) test pattern(s) in response to detecting taggedframes with predetermined metadata. As described herein, thepredetermined metadata may be metadata native to the image frame(s) orthe predetermined metadata may be a tag that is written into themetadata by the display system. In some embodiments, the DMA rendersdifferent test patterns in different locations within the signal inresponse to various triggers. For example, the DMA may render a testpattern in the blue channel in response to a visual trigger, asdescribed herein, or render a test pattern in the active region inresponse to a predetermined movement.

The test patterns rendered in the first signal and the second signal maybe sampled and compared by the DAT, as described herein, and one or moredifferentials are provided to the DMA. The one or more differentials,such as a coordinate differential, a dimensional differential, a colordifferential, or other differentials, are used by the DMA in shiftingpixels (1750) and/or adjusting (1760) color attributes of the firstsignal and/or second signal.

Embodiments of the present invention may comprise or utilize a specialpurpose or general-purpose computer including computer hardware, asdiscussed in greater detail below. Embodiments within the scope of thepresent invention also include physical and other computer-readablemedia for carrying or storing computer-executable instructions and/ordata structures. Such computer-readable media can be any available mediathat can be accessed by a general purpose or special purpose computersystem. Computer-readable media that store computer-executableinstructions are physical storage media. Computer-readable media thatcarry computer-executable instructions are transmission media. Thus, byway of example, and not limitation, embodiments of the invention cancomprise at least two distinctly different kinds of computer-readablemedia: physical computer-readable storage media and transmissioncomputer-readable media.

A “network” is defined as one or more data links that enable thetransport of electronic data between computer systems and/or modulesand/or other electronic devices. When information is transferred orprovided over a network or another communications connection (eitherhardwired, wireless, or a combination of hardwired or wireless) to acomputer, the computer properly views the connection as a transmissionmedium. Transmissions media can include a network and/or data linkswhich can be used to carry or desired program code means in the form ofcomputer-executable instructions or data structures and which can beaccessed by a general purpose or special purpose computer. Combinationsof the above are also included within the scope of computer-readablemedia.

Further, upon reaching various computer system components, program codemeans in the form of computer-executable instructions or data structurescan be transferred automatically from transmission computer-readablemedia to physical computer-readable storage media (or vice versa). Forexample, computer-executable instructions or data structures receivedover a network or data link can be buffered in RAM within a networkinterface module (e.g., a “NIC”), and then eventually transferred tocomputer system RAM and/or to less volatile computer-readable physicalstorage media at a computer system. Thus, computer-readable physicalstorage media can be included in computer system components that also(or even primarily) utilize transmission media.

Computer-executable instructions comprise, for example, instructions anddata which cause a general purpose computer, special purpose computer,or special purpose processing device to perform a certain function orgroup of functions. The computer-executable instructions may be, forexample, binaries, intermediate format instructions such as assemblylanguage, or even source code. Although the subject matter has beendescribed in language specific to structural features and/ormethodological acts, it is to be understood that the subject matterdefined in the appended claims is not necessarily limited to thedescribed features or acts described above. Rather, the describedfeatures and acts are disclosed as example forms of implementing theclaims.

Those skilled in the art will appreciate that the invention may bepracticed in network computing environments with many types of computersystem configurations, including, personal computers, desktop computers,laptop computers, message processors, hand-held devices, multi-processorsystems, microprocessor-based or programmable consumer electronics,network PCs, minicomputers, mainframe computers, mobile telephones,PDAs, pagers, routers, switches, and the like. The invention may also bepracticed in distributed system environments where local and remotecomputer systems, which are linked (either by hardwired data links,wireless data links, or by a combination of hardwired and wireless datalinks) through a network, both perform tasks. In a distributed systemenvironment, program modules may be located in both local and remotememory storage devices.

Alternatively, or in addition, the functionality described herein can beperformed, at least in part, by one or more hardware logic components.For example, and without limitation, illustrative types of hardwarelogic components that can be used include Field-programmable Gate Arrays(FPGAs), Program-specific Integrated Circuits (ASICs), Program-specificStandard Products (ASSPs), System-on-a-chip systems (SOCs), ComplexProgrammable Logic Devices (CPLDs), etc.

The articles “a,” “an,” and “the” are intended to mean that there areone or more of the elements in the preceding descriptions. The terms“comprising,” “including,” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements. Additionally, it should be understood that references to “oneembodiment” or “an embodiment” of the present disclosure are notintended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features. For example, anyelement described in relation to an embodiment herein is combinable withany element of any other embodiment described herein, unless suchfeatures are described as, or by their nature are, mutually exclusive.

Numbers, percentages, ratios, or other values stated herein are intendedto include that value, and also other values that are “about” or“approximately” the stated value, as would be appreciated by one ofordinary skill in the art encompassed by embodiments of the presentdisclosure. A stated value should therefore be interpreted broadlyenough to encompass values that are at least close enough to the statedvalue to perform a desired function or achieve a desired result. Thestated values include at least the variation to be expected in asuitable manufacturing or production process, and may include valuesthat are within 5%, within 1%, within 0.1%, or within 0.01% of a statedvalue. Where ranges are described in combination with a set of potentiallower or upper values, each value may be used in an open-ended range(e.g., at least 50%, up to 50%), as a single value, or two values may becombined to define a range (e.g., between 50% and 75%).

A person having ordinary skill in the art should realize in view of thepresent disclosure that equivalent constructions do not depart from thespirit and scope of the present disclosure, and that various changes,substitutions, and alterations may be made to embodiments disclosedherein without departing from the spirit and scope of the presentdisclosure. Equivalent constructions, including functional“means-plus-function” clauses are intended to cover the structuresdescribed herein as performing the recited function, including bothstructural equivalents that operate in the same manner, and equivalentstructures that provide the same function. It is the express intentionof the applicant not to invoke means-plus-function or other functionalclaiming for any claim except for those in which the words ‘means for’appear together with an associated function. Each addition, deletion,and modification to the embodiments that falls within the meaning andscope of the claims is to be embraced by the claims.

The terms “approximately,” “about,” and “substantially” as used hereinrepresent an amount close to the stated amount that still performs adesired function or achieves a desired result. For example, the terms“approximately,” “about,” and “substantially” may refer to an amountthat is within less than 5% of, within less than 1% of, within less than0.1% of, and within less than 0.01% of a stated amount. Further, itshould be understood that any directions or reference frames in thepreceding description are merely relative directions or movements. Forexample, any references to “up” and “down” or “above” or “below” aremerely descriptive of the relative position or movement of the relatedelements.

The present disclosure may be embodied in other specific forms withoutdeparting from its spirit or characteristics. The described embodimentsare to be considered as illustrative and not restrictive. The scope ofthe disclosure is, therefore, indicated by the appended claims ratherthan by the foregoing description. Changes that come within the meaningand range of equivalency of the claims are to be embraced within theirscope.

What is claimed is:
 1. A method of display alignment tracking for a head-mounted device, the method comprising: sampling a first signal from a first waveguide; sampling a second signal from a second waveguide; combining the first signal and second signal optically into a combined optical signal; detecting a test pattern within the combined optical signal, the test pattern being included within each of the first signal and the second signal; and comparing at least a first physical position corresponding to the test pattern within the first signal and a second physical position corresponding to the test pattern with the second signal to identify a differential between the first physical position and the second physical position.
 2. The method of claim 1, wherein comparing the first and second physical positions includes comparing pixel locations of the test pattern within the first signal and the second signal at a subpixel level and thereafter adjusting a rendering position for at least one of the first signal and the second signal.
 3. The method of claim 1, wherein the method further includes comparing a color level associated with a rendering of the first signal to a color level associated with a rendering of the second signal and thereafter adjusting a color level for rendering at least one of the first signal and the second signal.
 4. The method of claim 1, wherein the method further includes: providing the test pattern during a startup procedure of a display module assembly.
 5. The method of claim 1, wherein the method further includes providing the test pattern to a display pixel array, the display pixel array being configured to render the first signal and second signal, the display pixel array having active pixels and border pixels, and wherein providing the test pattern includes the display pixel array rendering the test pattern in the border pixels.
 6. The method of claim 5, wherein the method further includes: shifting a location of the active pixels within the display pixel array based at least partially upon a differential in a rendering position of the first signal and the second signal.
 7. The method of claim 1, wherein method further includes providing the test pattern with a display module assembly in the first signal and the second signal includes and by interleaving at least one test pattern frame within a plurality of other image frames being provided with the display module assembly.
 8. The method of claim 1, wherein the method further includes providing the test pattern in a blue channel.
 9. The method of claim 1, wherein the method further includes providing the test pattern by at least tagging image frames with test pattern metadata and by providing the test pattern separately from the image frames, and by inserting the test pattern in response to detecting receipt of the test pattern metadata during rendering of the image frames.
 10. The method of claim 1, wherein the method includes detecting a predetermined movement of the head-mounted device and in response to the predetermined movement, providing the test pattern for rendering with the first signal and the second signal.
 11. The method of claim 1, wherein the method further includes: identifying a first color attribute associated with rendering the first signal and a corresponding second color attribute associated with rendering the second signal; calculate a differential between the first and second color attribute; and use the differential to adjust at least one of the first signal and the second signal.
 12. A display alignment tracking system for tracking signal alignment in waveguides, the system comprising: at least one display module assembly configured to provide a first signal and a second signal; a first waveguide configured to guide the first signal therethrough; a second waveguide configured to guide the second signal therethrough; an optical multiplexer in optical communication with the first waveguide and the second waveguide, the optical multiplexer configured to combine at least a portion of the first signal and at least a portion of the second signal; an imaging sensor in optical communication with the optical multiplexer and configured to receive a combined signal from the optical multiplexer that includes at least a portion of the first signal and at least a portion of second signal; one or more processors in data communication with the imaging sensor; and one or more computer-readable media having stored thereon instructions that are executable by the one or more processors to perform at least the following: receive at least a portion of the first signal and at least a portion of the second signal from the imaging sensor; identify a first pattern included in the first signal and a second pattern included in the second signal; and compare at least physical positioning of the first pattern relative to at least physical positioning of the second pattern.
 13. The system of claim 12, wherein one or more computer-readable media further have stored thereon instructions that are executable by the one or more processors to configure the computer system to perform at least the following: calculate a displacement value of the first pattern and second pattern; and provide the displacement value to a display module assembly.
 14. The system of claim 12, wherein one or more computer-readable media further have stored thereon instructions that are executable by the one or more processors to configure the computer system to perform at least the following: provide a test pattern with the display module assembly in the first signal and the second signal, the first pattern and the second pattern comprising at least a portion of the test pattern.
 15. The system of claim 14, wherein providing the test pattern with the display module assembly in the first signal and the second signal includes providing the test pattern during a startup procedure of the display module assembly.
 16. The system of claim 14, further comprising a display pixel array in communication with the display module assembly, wherein providing the test pattern includes providing the test pattern to the display pixel array, the display pixel array being configured to render the first signal and second signal, the display pixel array having active pixels and border pixels, and wherein providing the test pattern with the display module assembly in the first signal and the second signal includes the display pixel array rendering the test pattern in the border pixels.
 17. The system of claim 16, wherein one or more computer-readable media further have stored thereon instructions that are executable by the one or more processors to configure the computer system to perform at least the following: calculate a displacement value of the first pattern and second pattern; provide the displacement value to a display module assembly; and shift a location of the active pixels within the display pixel array based at least partially upon the displacement value.
 18. The system of claim 14, wherein providing the test pattern with the display module assembly in the first signal and the second signal includes interleaving a test pattern frame within a plurality of other image frames being provided with the display module assembly.
 19. The system of claim 14, wherein providing the test pattern with the display module assembly in the first signal and the second signal includes providing the test pattern in a blue channel.
 20. The system of claim 12, wherein one or more computer-readable media further have stored thereon instructions that are executable by the one or more processors to configure the computer system to perform at least the following: identify a color attribute of the first pattern and a corresponding color attribute of the second pattern; calculate a differential between the color attribute of the first pattern and the corresponding color attribute of the second pattern; and use the differential to adjust at least one of the first signal and the second signal. 